Method of forming insulated wire



March 27, 1962 W, HAMMER ETAL METHOD OF FORMING INSULATED WIRE Filed Jan. 16, 1961 NWI wnrn. @2.4000

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,United States "Patent 3,027,287 METHOD OF FORMING INSULATED WIRE Warren Hammer, Hillside, and Chester F. Sudds,

Wheaton, Ill., assiguors to Belden Manufacturing Cornpany, Chicago, Ill., a corporation of Illinois Filed Jan. 16, 1961, Ser. No. 82,772 3 Claims. (Cl. 156-56) This invention relates to a method of forming insulated wire and more particularly to a method of forming insulated wire which is generally known in the trade as textile-wrapped, enameled magnet wire. l

A textile-wrapped, enameled magnet wire includes an electrical conducting wire which is coated with a layer or film of enamel, using the word enamel in its broad sense as including any kind of lacquer or varnish or any of the usable synthetic insulations or other type of plastic substance as contrasted with textile coverings such as strands of silk, cotton or other natural or synthetic fibers. A textile covering generally known as a serving is applied over the enamel coating by wrapping or braiding and has as its main purpose the protection of the wire against mechanical abuse, coupled with some insulating value.

In the manufacture of insulated conductors having an enamel coating protected `by a textile serving, it is desirai ble that the textile serving should be bonded or anchored in some way to the enamel layer or the surface thereof, so that if the wire is cut or damaged, the textile strands, individually or otherwise, will not fray or become unwrapped, and so that if any accident does result in a localized injury to the serving, such injury will be localized to that particular spot and Will not extend further than the immediate injury.

Although attempts have been made to solve this problem, either the results have not been entirely satisfactory, or the cost of solving the problem has introduced manufacturing difficulties and other problems involved in the use of the product, or the expense of overcoming the difficulty has been out of line with the value of the product.

This application is a continuation-in-part of our copending application, Serial No. 755,213, liled August l5, l958, now Patent No. 2,970,937, issued February 7, 1961.

The principle object of the present invention is to provide a textile-covered, enameled magnet wire having a covering of high dielectric strength, of reasonable thickness and able to withstand the mechanical abuse to which wires of this class are subjected in the course of manufacture of the wire and vin the use of the product.

Further objects of the invention are to enable a product of the desired quality to be manufactured by the use of types of machinery and other facilities and available materials so that the desired result can be obtained at a reasonable cost.

In the accompanying drawings, which illustrate the improved process by means of which the foregoing desirable results are obtained:

FIGURE 1 is a diagrammatic ow sheet showing broadly the various steps utilized in practicing the process; and

FIGURE 2 is also a diagrammatic View in somewhat more detail, showing more specifically the apparatus ernployed in practicing the process.

Referring to the drawings, and rst to FIGURE 1, it will be seen that a coating A of enamel insulation is applied to the -bare conductor wire and dried. The enameled wire 11 then travels to the next step of the process where there is applied a second coating B on top of the enamel insulation A, said second coating B being also of the enamel type, but dilfering in composition from the insulation A in that the B coating is softenable by 3,027,287 Patented Mar. 27, 1962 heat (thermoplastic) as to which the lirst coating A is practically insensitive.

The wire 12 which now includes the first two coatings is then conducted to the next stage of the process where there is applied a wrap C of textile material such as has been described. At that point of the process, the textile wrap is retained on the wire 12 merely -by reason of the fact that it is wrapped tightly, and preferably spirally, around the wire yby the serving apparatus.

The wire 13, which has been subjected to the first three steps of the process, i.e., A, B and C, is then passed through an oven or otherwise heated to soften the second coating and make it tacky for a suicient length of time to anchor or bond the textile serving to the outer surface of the second enamel coating. The second coating is then hardened by permitting the completed product 14 to harden naturally or, if necessary, by propelling the wire through a cooling zone.

In the nished product 14, the second or intermediate thermoplastic coating B constitutes a cementitious anchor or autogenous bond between the primary inner enamel coating A and the outer textile covering C.

In FIGURE 2 or the drawings, which illustrates the equipment employed in one particular application of the invention, the bare wire 10 is shown as coming from the bare wire supply spool as indicated at 1S to one of a set of sheaves 16 from which the wire travels downwardly to a lower set of sheaves 17 dipping into a trough 18 containing a supply of enameling liquid. Various types of enamel may be employed, as previously described, but we have found good commercial results from the use of reaction polymers o the polyurethane and also vinyl acetal types in a conventional vehicle such as cresylic acid with a suitable amount of a conventional aromatic hydrocarbon solvent,

As is customary in the use of various types of enamels,

the wire travels around a number of sheaves, each up-V ward pass being through an oven 19 heatedto the proper degree to bake or set the film or coating of enamel onthe wire or on the previous iilm, as the case maybe.

When the bare wire has received enough coatings, the enameled wire 11 then goes to a second enameling apparatus, similar to the one previously described, and including a set of upper sheaves 20 and a set of lower sheaves 21 dipping into a trough 22 in which there yis contained a bath of thermoplastic insulation. For example, a solution of polyvinyl butyr-al in the same type of solvent as is used as a vehicle for the enamel coating A, has been successfully employed to good advantage.y

In its upward travel between the sheaves 20 and 21, the wire passes through an oven or drier 23.

The Wire 12 carrying the inner enamel coating the superposed thermoplastic coating B then passes around a sheave 24 and upwardly through a textile insulating head indicated diagrammatically at 25. 'Ihis may be of the conventional type employing an outer bowl 26 rotating at high speed and containing a tube of textile insulation, for example, in this instance cotton 27, which is applied to the wire 12 by means of an upwardly extending linger or other device 28 rotating with the bowl 26, the linear speed of the wire and the r.p.m. of the head being coordinated so that the spiral serving or wrap applied to the wire will not overlap at its edges and nevertheless will leave no significant space between adjacent turns or spirals of the serving.

The wire 13 which then carries the first enamel coating, the second thermoplastic coating and the cotton serving, then passes over a guide spool 29 down to an oven 31, wherein the thermoplastic coating is softened. After the wire .13 passes around a sheave l32 in the oven, it passes upwardly through a pipe 33 which, if necessary, may be cooled slightly in order to harden the thermoon the4 coated wire also enhances the plastic.- The temperature in the oven and the exposure time ofthe coated wire in the oven vdepends upon the size of wire, type of material in the coatings, etc. The wire then passes to a spool 34 on which the wire is wound by asuitable-apparatus (not shown). y

In certain applications, the coatedV wire-may be ypassed v directly 'from `the textile insulating head to the. spool and Vthenthespool of Wire may be heated to soften the thermoplastic coating. For example, spools of the coated wire in the smaller sizes, such-as 24-gauge are heated approXim'ately four' hours at 250 F. to effect bonding.A

In vanother embodiment of the method, an additional coating kof thermoplastic insulation is applied over the textile wrap C prior to the heating operation. Subsequent heat-ng of this'coated ,wirev causes the two coatings B and D to flow towardea'ch other through the wrap C resulting in a-stronger bond'. The additional coating D l physical and dielectric properties of the finished wire.

The additional coating D may-be applied in a similiar 'manner' to that described in connection with the application of the second coating B andthe coating may be of thelsame thermoplastic material; The two coatings B and D arev softened prior to' being wound on a spool.

The foregoingi'process has been successfully used in producing an improved typev of textile-covered enameled magnet wire in sizes ranging from No. 8 to No. 40. The process khas the particular manufacturing advantage that, in applying theftextile serving, the normal operation of the servingv head isfn'ot interfered with and proceeds with its usual efficiency, without any need to clean' the headfroni timeto time from accumulations of sticky ad- -1sive material. Also the final step of applying heat to thejcoatedfwire" doesf'not present any signicant problem.

Theiprod'lic't produced 'by thefo'regoing process is ofv which pro'c'evsswcor'npr'ise's first' coating a mietallicwire withY at' plastic dielectric enanreling4 substance, Vand drying saidY dielectric'coating'to' provide an enamel coating which is 'therinlly' insensitive 'during the remainder of the process', then Iapplyinga thermoplastic substance to' said coatedwife to provide a'second coating of a material which' is capableof being softened by"he"at employed in a later step of the process and drying said secondV coating, -then applying `a porous textile serving over said second coating, then subjecting said product to heat which softens said second coating, but does not affect said first coating, and subsequently permitting said second coating to harden so as to effect a cementitious bond between said second coating and the inner surface of the serving while retaining the original properties of said first coating and said serving.

2. The process of making textile-wrapped magnet Wire having inherent superior ability toV prevent unraveling of the textile wraprprior tothe use of the process product, which process comprises first coating a fmetallic wire by passing 4it through a bath of a plastic dielectric substance which, when dried, is insensitive to heat, and drying said coating, then passing said coated'wire through a bath of a thermoplastic substance `which, after drying, is softenable by heat so as tovprovide'a second coating lbonded to said first coating, and drying said coating, then applyingV a porous textile servingl over said second coating, then winding said textile coated wire on a` spool, then subjecting said lproduct to heat so that it will penetrate said outer serving and partially soften said second coating, but not affect the'frs't coating and subsequently permitting said second coating to harden so astoeffect a ceme'nti. tious bond between the second coating and the inner surface of said serving.

3. The process of making textile-wrapped magnet wire having inherent superior ability to prevent unraveling of Y the textile wrap priorto the use of the process product, which process'comprises, first coating a metallic wire with a plastic dielectric enameling substance, and drying said `dielectric coating lto provide an enamel coating which is thermally insensitive during the remainder of the process,

then' applying a thermoplasticY substance to' said coated wire to provide a`v second coating of a material which' is" capable of being softenedl byheat employed in aIv latery step ofthe process', anddrying said secondv coating, then applying" aY porous textile serving over saidn .second coating, then applying an additional coating of a thermoplastic' substance'to said serving to provide a fourth Ycoating Y of a materialv capable of being 'softenedby heat,` and drying' 'said vfourth coating, .then subjecting saidproduct `to heat which` softens said second and fourth coatings, but doe's not affect 'said'first coating, and subsequently-permitting said secondand fourth' coatings to harden so as to effect a'cementitious bond between said second coating and the Vinner surface of the serving and, between said fourth coating and the Vouter surface,A ofv the serving while 'retaining the original properties of said first' coating and said serving.

No referencescited. 

1. THE PROCESS OF MAKING TEXTILE-WRAPPED MAGNET WIRE HAVING INHERENT SUPERIOR ABILITY TO PREVENT UNRAVELING OF THE TEXTILE WRAP PRIOR TO THE USED OF THE PROCESS PRODUCT, WHICH PROCESS COMPRISES FIRST COATING A METALLIC WIRE WITH A PLASTIC DIELECTRIC ENAMELING SUBSTANCE, AND DRYING SAID DIELECTRIC COATING TO PROVIDE AN ENAMEL COATING WHICH IS THERMALLY INSENSITIVE DURING THE REMAINDER OF THE PROCESS, THEN APPLYING A THERMOPLASTIC SUBSTANCE TO SAID COATED WIRE TO PROVIDE A SECOND COATING OF A MATERIAL WHICH IS CAPABLE OF BEING SOFTENED BY HEAT EMPLOYED IN A LATER STEP OF THE PROCESS AND DRYING SAID SECOND COATING, THEN APPLYING A POROUS TEXTILE SERVING OVER SAID SECOND COATING, THEN SUBJECTING SAID PRODUCT TO HEAT WHICH SOFTENS SAID SECOND COATING, BUT DOES NOT AFFECT SAID FIRST COATING, AND SUBSEQUENTLY PERMITTING SAID SECOND COATING TO HARDEN SO AS TO EFFECT A CEMENTITIOUS BOND BETWEEN SAID SECOND COATING AND THE INNER SURFACE OF THE SERVING WHILE RETAINING THE ORIGINAL PROPERTIES OF SAID FIRST COATING AND SAID SERVING. 